1. Field of the Invention
The present invention relates to an image display apparatus called a head-mounted display or the like, an image display system, and an image display element.
2. Related Background Art
Various types of head-mounted displays have been proposed, which are mounted on the heads or faces of observers to allow them to enjoy images and sounds with great enthusiasm.
A conventional head-mounted display will be described below with reference to FIGS. 29 and 30. A head-mounted display 701 is comprised of a main body 711, band portions 712 formed on the left and right sides of the main body 711, and a bridge 713 formed on the main body 711, and is mounted on the face of an observer like a pair of glasses.
The main body 711 has the image display unit 714 shown in FIG. 30 which is held by a housing 710. A transmissive liquid crystal display element (LCD) 702 displays two-dimensional images. A backlight 703 illuminates the LCD 702. As the backlight 703, a planar fluorescent tube is used. An electric board 704 is used to drive the LCD 702 and backlight 703. An observation prism 705 guides the image displayed on the LCD 702 to an eye 720 of the observer.
The image displayed on the LCD 702 is transmitted through a third surface 708 of the observation prism 705 first, and then totally reflected by a first surface 706. The image light reflected by the first surface 706 is reflected by a second surface 707 of the observation prism 705 again. Thereafter, the image light is transmitted through the first surface 706 and projected on the eye 720 of the observer.
Note that the first surface 706 has a portion that totally reflects image light and a portion through which light is transmitted. The portion that totally reflects image light may be designed to satisfy a total reflection condition by using the difference in refractive index between the observation prism 705 and air. Alternatively, a reflecting film may be formed only within a reflection range by vapor deposition.
According to the head-mounted display having the above arrangement, the image displayed on the LCD 702 can be enlarged by the observation prism 705, and the user can observe the enlarged image (as if he/she watched it on the screen in a movie theater or on the large screen of a TV set).
In this head-mounted display, however, the light emitted from the LCD 702 partly strikes a portion other than the optical effective portion of the observation prism 705 to cause flare and ghosts.
For this reason, an arrangement is disclosed in Japanese Patent Application Laid-Open No. 9-65245, in which the light emerging from the observation prism 705 is partly blocked by a light-shielding plate 717 to prevent flare light and ghost light from reaching the eye 720 of the observer.
In the image display apparatus disclosed in the above reference, however, the light-shielding plate 717 is positioned on the premise that the eyes of the observer are always kept at predetermined positions. If, therefore, the positions of the eyes deviate, flare light and ghost light may be guided to the eyes.
Recently, an image display apparatus has been proposed, which uses a reflective LCD capable of displaying images with higher resolution and higher quality than a transmissive LCD and coping with images output from a PC, DVD player, or the like.
An image display apparatus using such a reflective LCD is disclosed in Japanese Patent Application Laid-Open No. 11-125791. In this apparatus, as shown in FIG. 31, light beams from a light source directly illuminate the reflective LCD, and an image from the reflective LCD is enlarged and displayed as a virtual image by a prism-like optical element to be guided to the eyes of the observer.
In this case, however, the illumination light that illuminates the reflective LCD irradiates the effective image display area on the LCD and a portion outside the area, and reflected light that is unnecessary for image display is also guided to the eyes of the observer. Owing to such unnecessary light, a peripheral portion of the image looks excessively bright or the contrast of the image decreases, resulting in flare, ghosts, and the like. This makes it impossible to observe excellent images.
It is an object of the present invention to provide an image display apparatus which can effectively remove unnecessary light in image display to improve uniformity of illumination on an image display element and effectively prevent a decrease in the contrast of images and occurrence of flare and ghosts, thereby allowing observation of excellent images.
In order to achieve the above object, according to the present invention, there is provided an image display apparatus comprising a light source for emitting illumination light, an image display element for displaying an image by reflecting the illumination light incident thereon, an illumination optical element which reflects the illumination light from the light source toward the image display element and through which image light from the image display element is transmitted, an observation optical element for guiding the image light transmitted through the illumination optical element to an eye of an observer, and a light-shielding member for blocking at least one of unnecessary light which is contained in the illumination light from the light source and travels outside an effective image display area of the image display element and unnecessary light which is contained in the image light from the image display element and travels outside an effective observation space.
In addition, according to the present invention, there is provided an image display system including an image display apparatus and an image information supply apparatus for supplying image information to the image display apparatus, comprising a light source for emitting illumination light, an image display element for displaying an image by reflecting the illumination light incident thereon, an illumination optical element which reflects the illumination light from the light source toward the image display element and through which image light from the image display element is transmitted, an observation optical element for guiding the image light transmitted through the illumination optical element to an eye of an observer, and a light-shielding member for blocking at least one of unnecessary light which is contained in the illumination light from the light source and travels outside an effective image display area of the image display element and unnecessary light which is contained in the image light from the image display element and travels outside an effective observation space.
Furthermore, according to the present invention, there is provided an image display element for displaying an image by reflecting incident light in an observation side space, comprising a light control layer for controlling transmission/non-transmission of illumination light in accordance with an input image signal, a reflecting layer provided on a rear surface side of the light control layer, and a light-shielding member for blocking incident light, of obliquely applied light, which travels outside an effective image display area of the image display element, and also blocking reflected light outside an effective observation space of the observation side space.
The above and other objects, features, and advantages of the present invention will be apparent from the following detailed description in conjunction with the accompanying drawings and the appended claims.